docs: def sha1sum_file(filename):
      '''
      Return the secure hash digest with sha1 algorithm for a given file
  
      >>> from timeside.core.tools.test_samples import samples
      >>> wav_file = samples["C4_scale.wav"]
      >>> print sha1sum_file(wav_file)
      a598e78d0b5c90da54a77e34c083abdcd38d42ba
      '''
      import hashlib
      import io
  
      sha1 = hashlib.sha1()
      chunk_size = sha1.block_size * io.DEFAULT_BUFFER_SIZE
  
      with open(filename, 'rb') as f:
          for chunk in iter(lambda: f.read(chunk_size), b''):
              sha1.update(chunk)
      return sha1.hexdigest()